power train, vehicle and methods

ABSTRACT

A powertrain is adapted to drive ground-engaging elements disposed along longitudinally-opposing sides of a vehicle. The powertrain includes at least one engine, a first electric machine, a second electric machine, a third electric machine, a first differential mechanism and a second differential mechanism. The engine and first electric machine are operatively connected to the first and second differential mechanisms. The second electric machine is operatively connected to the first differential mechanism and the third electric machine is operatively connected to the second differential mechanism. The first and second differential mechanisms are each operatively connected to drivably engage one or more ground-engaging elements disposed on a different one of the longitudinally-opposing sides of the associated vehicle. A vehicle including such a powertrain as well as methods of using the same are also included.

This application claims priority from U.S. Provisional PatentApplication No. 60/851,537 filed on Oct. 13, 2006, which is herebyincorporated herein by reference in its entirety.

BACKGROUND

The subject matter of the present disclosure broadly relates to the artof vehicle powertrains and, more particularly, to anelectrically-variable powertrain for an all-wheel drive vehicle. Thesubject matter finds particular application and use in conjunction withhigh-performance, all-terrain personnel transport vehicles, and will bedescribed herein with particular reference thereto. However, it is to beappreciated that the subject matter of the present disclosure is alsoamenable to use in other applications and environments, such as inpassenger vehicles, light-duty trucks, sport-utility vehicles and othertransport vehicles, for example. Thus, it will be appreciated that anyspecific reference herein to use in association with high-performance,all-terrain personnel transport vehicles is merely exemplary.

It will be appreciated that the present disclosure includes numerousrotating components (e.g., rotors, crankshafts, axles, gears) that canrotate at different speeds, rotate in different directions, transmit orcarry different torsional loads, and/or transmit or carry differenthorsepower loads, as either inputs or outputs. For ease of reading andunderstanding, terms such as rotational connection, rotational output,rotational power source, and the like, have been used to broadly referto any such rotational, torsional or power condition. Additionally, asused herein with reference to certain elements, features, components,structures and/or actions (e.g., “first electric machine,” “secondelectric machine,” “first rotational connection” and “second rotationalconnection”), numerical ordinals merely denote different singles of aplurality and do not imply any order or sequence unless specificallydefined by the claim language.

Personnel transport vehicles of a variety of types and kinds are knownand commonly used. In many of such known vehicles, the powertrain andother mechanical components are centrally located on the vehicletypically toward the bottom side thereof. It is well recognized thatcomponents of greater size and/or mass are often less significantlydamaged by projectiles and the discharge from explosive ordinance thanare components of lesser size and/or mass. Though known arrangementsprovide some additional shielding against discharges from ordinancepositioned underneath the vehicle, known arrangements do not utilize themass of the powertrain components as supplemental shielding of thepersonnel compartment of the vehicle.

Additionally, known hybrid powertrains typically control the supply ofmotive power to the vehicle under an axle-by-axle type of operation.This is believed to be the case even when such a hybrid powertrain isused on an all-wheel drive vehicle. As such, as a vehicle is travelingon a succession of dry and icy surfaces, there is often only a smallinterval during which the axles are operating under different conditionsfrom one another. As a vehicle is traveling along a partiallysnow-covered road, one side of the vehicle may be operating on drypavement while the other side of the vehicle may be operating on snowand ice. Under such conditions, known hybrid powertrains are believed toprovide less than optimal control of the vehicle.

Furthermore, known hybrid vehicles commonly operate in a manner thatresults in asymmetrical cornering of the vehicle. That is, thesevehicles are believed to operate such that the front and rear wheels ofthe vehicle track along slightly different paths as the vehiclenegotiates a turn or corner. In some circumstances, such operation maybe undesirable because it could be possible for one wheel on one side ofthe vehicle to avoid hitting an object laying on the ground while thesecond wheel on that side of the vehicle might contact the object, suchas during a cornering maneuver, for example.

Accordingly, it is believed desirable to develop anelectrically-variable powertrain for an all-wheel drive vehicle as wellas methods of operation that may overcome one or more of the foregoingand other disadvantages.

BRIEF DESCRIPTION

A vehicle in accordance with the present novel concept is provided thatincludes a vehicle structural assembly having a longitudinally-extendingcenterline with first and second vehicle structure portions extendingalong opposing sides of the centerline. A first plurality ofground-engaging elements is operatively disposed along the first vehiclestructure portion on one of the opposing sides of the centerline. Asecond plurality of ground-engaging elements is operatively disposedalong the second vehicle structure portion on the other of the opposingsides of the centerline. A vehicle powertrain drivably engages one ormore ground-engaging elements of each of the first and secondpluralities of ground-engaging elements. The vehicle powertrain includesat least one engine that includes an engine rotational connection. Thevehicle powertrain also includes a first electric machine. The firstelectric machine includes a first EM rotational connection that isoperatively connected to the engine rotational connection. The vehiclepowertrain also includes second and third electric machines. The secondelectric machine includes a second EM rotational connection and thethird electric machine includes a third EM rotational connection. Thevehicle powertrain further includes first and second differentials. Thefirst differential includes first, second and third DF rotationalconnections. The first DF rotational connection is operatively connectedto the engine rotational connection and the first EM rotationalconnection. The second DF rotational connection is operatively connectedto the second EM rotational connection. The third DF rotationalconnection is operatively connected to drivably engage the firstplurality of ground-engaging elements on one opposing side of thecenterline. The second differential includes fourth, fifth and sixth DFrotational connections. The fourth DF rotational connection isoperatively connected to the engine rotational connection and the firstEM rotational connection. The fifth DF rotational connection isoperatively connected to the third EM rotational connection. The sixthDF rotational connection is operatively connected to drivably engage thesecond plurality of ground engaging elements on the other opposing sideof the centerline.

A powertrain in accordance with the present novel concept that isadapted to drive associated ground-engaging elements disposed alonglongitudinally-opposing sides of an associated vehicle is provided thatincludes at least one engine having an engine rotational connection. Afirst electric machine includes a first EM rotational connection that isoperatively connected to the engine rotational connection. A secondelectric machine includes a second EM rotational connection and a thirdelectric machine includes a third EM rotational connection. A firstdifferential mechanism includes first, second and third DF rotationalconnections. The first DF rotational connection is operatively connectedto the engine rotational connection and the first EM rotationalconnection. The second DF rotational connection is operatively connectedto the second EM rotational connection. The third DF rotationalconnection is operatively connected to drivably engage one or more ofthe associated ground-engaging elements disposed on onelongitudinally-opposing side of the associated vehicle. A seconddifferential mechanism includes fourth, fifth and sixth DF rotationalconnections. The fourth DF rotational connection is operativelyconnected to the engine rotational connection and the first EMrotational connection. The fifth DF rotational connection is operativelyconnected to the third EM rotational connection. The sixth DF rotationalconnection is operatively connected to drivably engage one or moreassociated ground-engaging elements disposed on the otherlongitudinally-opposing side of the associated vehicle.

A method of powering of vehicle in accordance with the present novelconcept is provided that includes providing a vehicle structuralassembly including a longitudinally-extending centerline and opposingvehicle structure sides. The method also includes providing first andsecond pluralities of ground-engaging elements with the first pluralityof ground-engaging elements disposed along one opposing vehiclestructure side and the second plurality of ground-engaging elementsdisposed along the other opposing vehicle structure side. The methodalso includes providing a vehicle powertrain including a first engine, afirst electric machine, a second electric machine, a third electricmachine, and first and second differentials. The method further includestransmitting rotational output from at least the first engine to thefirst and second differentials. The method also includes transmittingrotational output from at least one of the first electric machine andthe second electric machine to the first differential and transmittingrotational output from at least one of the first electric machine andthe third electric machine to be second differential. The method furtherincludes transmitting rotational output from the first differential tothe first plurality of ground-engaging elements to operatively drive oneof the opposing vehicle structure sides and transmitting rotationaloutput from the second differential to the second plurality ofground-engaging elements to operatively drive the other of the opposingvehicle structure sides.

A method of generating electrical power from a vehicle is provided thatincludes providing a vehicle structural assembly including alongitudinally-extending centerline and opposing vehicle structuresides. The method also includes providing first and second pluralitiesof ground-engaging elements with the first plurality of ground-engagingelements disposed along one of the opposing vehicle structure sides andthe second plurality of ground-engaging elements disposed along theother of the opposing vehicle structure sides. The method furtherincludes providing a vehicle powertrain that includes a first engine, afirst electric machine, a second electric machine, a third electricmachine, and first and second differentials. The method also includesrotationally affixing the first and second pluralities ofground-engaging members such that rotational output from the first andsecond differentials can be respectively transmitted to the second andthird electric machines. The method further includes transmittingrotational output from at least the first engine to at least one of thefirst electric machine, the first differential and the seconddifferential. The method also includes generating electrical power at atleast one of the first, second and third electric machines in responseto the rotational output from the first engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of one exemplary embodiment of apowertrain in accordance with the present novel concept shownoperatively disposed on a vehicle.

FIG. 2 illustrates one exemplary method of powering a vehicle inaccordance with the present novel concept.

FIG. 2A illustrates another exemplary method of powering a vehicle inaccordance with the present novel concept.

FIG. 3 is a schematic representation of another exemplary embodiment ofa powertrain in accordance with the present novel concept shownoperatively disposed on a vehicle.

FIG. 4 illustrates still another exemplary method of powering a vehiclein accordance with the present novel concept.

FIG. 5 is a schematic representation of still another exemplaryembodiment of a powertrain in accordance with the present novel conceptshown operatively disposed on a vehicle.

FIG. 6 illustrates yet another exemplary method of powering a vehicle inaccordance with the present novel concept.

FIG. 6A illustrates a further exemplary method of powering a vehicle inaccordance with the present novel concept.

FIG. 6B illustrates still a further exemplary method of powering avehicle in accordance with the present novel concept

FIG. 7 is a schematic representation of a further exemplary embodimentof a powertrain in accordance with the present novel concept shownoperatively disposed on a vehicle.

FIG. 8 illustrates yet a further exemplary method of powering a vehiclein accordance with the present novel concept.

FIG. 8A illustrates a method of generating electrical power using avehicle that includes a powertrain in accordance with the present novelconcept.

DETAILED DESCRIPTION

Turning now to the drawings wherein the showings are for the purpose ofillustrating exemplary embodiments of the present novel concept andwhich are not intended as a limitation of the same, FIGS. 1, 3, 5 and 7each illustrate a vehicle that includes a vehicle structural assembly,such as a vehicle body, frame or chassis, for example. The vehiclesinclude longitudinally-spaced first or forward ends FND and second orrearward ends RND and are also shown as including alongitudinally-extending centerline CTL that generally defines opposingfirst and second sides SD1 and SD2 of the vehicle.

The vehicle structural assemblies can be supported on an unsprung massthat can include a plurality of ground-engaging elements, such as wheelsor linked tracks, for example, that are supported along each of opposingsides SD1 and SD2 of the vehicle. The unsprung mass can also include oneor more structural members or other components, such as support arms(not shown), for example, operatively connecting the plurality ofground-engaging elements to the vehicle structural assembly. It will beappreciated that the pluralities of ground-engaging elements (e.g.,wheels or linked tracks) as well as the structural members or othercomponents operatively connecting the pluralities of ground-engagingelements to the sprung mass of the vehicle (e.g., a vehicle structuralassembly) can be of any suitable type, kind and/or configuration.

Furthermore, the plurality of ground-engaging elements of the vehiclesin each of FIGS. 1, 3, 5 and 7 is shown as including fourground-engaging elements with two of the ground-engaging elementsdisposed along each of the two opposing sides SD1 and SD2. However, itwill be appreciated that any suitable number of ground-engaging elementscould alternately be used. In the exemplary embodiments shown, the fourground-engaging elements are spaced from one another such that oneground-engaging element is disposed toward the forward and rearwardcorners of each of the opposing sides of the vehicle. Thus, the vehiclein FIG. 1 is also shown with a midpoint MPT disposed along centerlineCTL approximately midway between the forward and rearwardground-engaging elements. It will be appreciated that the vehicles inFIGS. 3, 5 and 7 will have similar midpoints, though the same are notshown in the drawing figures.

With more specific reference to FIG. 1, a vehicle 100 includes a vehiclestructural assembly 102 with a first plurality of ground-engagingelements, such as wheels 104A and 104B, for example, disposed alongfirst side SD1 and a second plurality of ground-engaging elements, suchas wheels 104C and 104D, for example, disposed along second side SD2.Vehicle 100 also includes a powertrain 106 that is supported on vehiclestructural assembly 102 and is operatively connected to drivably engagethe plurality of ground-engaging elements (e.g., wheels 104A-D).

Powertrain 106 includes an engine 108 that is supported on or alongstructural assembly 102, and can be of any suitable type, kind and/orconfiguration. For example, engine 108 could be an internal combustionengine having one or more reciprocating pistons or, alternately, couldbe a rotary internal combustion engine. Additionally, engine 108 can beoperable on any type or kind of fuel, such as gasoline, diesel,hydrogen, ethanol, biodiesel, for example, or any other suitable fuelsor combination of fuels. Furthermore, an engine operating on a differentthermodynamic cycle could alternately be used, such as a sterling cycleengine, for example. In one embodiment, engine 108 is a multi-cylinderinternal combustion engine having an output power within a range of fromabout 50 hp to about 1000 hp. Additionally, normally aspirated enginesor, alternately, engines utilizing forced air induction (e.g.,turbo-charging, super-charging) can be used.

Powertrain 106 also includes a first, second and third electricmachines, which are indicated in FIG. 1 by reference numbers 110, 112and 114, respectively. The first, second and third electric machines aresupported on or along structural assembly 102 in a suitable manner.Additionally, the first, second and third electric machines can be ofany suitable type, kind or construction, and can include any suitableperformance characteristics or specifications. Furthermore, the first,second and third electric machines can be of the same or different size,speed and/or power output relative to one another. In one exemplaryembodiment, the second and third electric machines are substantiallysimilar to one another and have a nominal power output that isapproximately half the nominal power output of the first electricmachine. In another exemplary embodiment, the second and third electricmachines can have a nominal power output that is approximatelyone-quarter of the nominal power output of the first electric machine.

Engine 108 includes an engine rotational connection 116 and canoptionally include a clutch (not shown) for selectively disengaging theengine from rotational connection 116. First electric machine 110includes a first EM rotational connection 118. In the exemplaryembodiment shown, the engine and the first electric machine aresupported on or along vehicle structural assembly 102 in approximatelyparallel relation such that engine rotational connection 116 and firstEM rotational connection 118 are disposed adjacent one another. A firsttransmission 120 is operatively connected between engine rotationalconnection 116 and first EM rotational connection 118. In the exemplaryembodiment shown, first transmission 120 is a fixed ratio transmissionthat is operable to maintain a ratio of angular velocities between theengine and the first electric machine. It will be appreciated that theratio of the first transmission can be selected based upon the desiredoutput and other performance characteristics of a given applicationand/or use of powertrain 106. Alternately, a variable ratio transmissioncould optionally be used. In either case, first transmission 120includes a rotational connection 122 that transmits the resulting orcombined rotational output from the engine and first electric machine.

Powertrain 106 also includes first and second differentials ordifferential mechanisms 124 and 126. First differential 124 includesthree rotational connections, which are respectively referred to hereinas first, second and third rotational connections 128, 130 and 132.Similarly, second differential includes three rotational connections,which are respectively referred to as fourth, fifth and sixth rotationalconnections 134, 136 and 138. In the embodiment shown in FIG. 1, theresulting output from the engine and the first electric machine isdelivered from rotational connection 122 to first and seconddifferentials 124 and 126. It will be appreciated that the transmissionof the resulting rotational output to the first and second differentialscan be achieved in any suitable manner. For example, a secondtransmission 140 that includes suitably sized transmission elements(e.g., gears) can be operatively connected between rotational connection122 and the first and fourth rotational connections of the first andsecond differentials, respectively. In one exemplary embodiment, it maybe desirable to transfer the resulting rotational output from the engineand the first electric machine equally between the first and seconddifferentials. In such case, second transmission 140 can include twosubstantially identical gears that are operatively interconnectedbetween rotational connection 122 and rotational connections 128 and134. In practice first transmission 120 ad second transmission 140 canbe located or otherwise disposed in a common housing (not shown).

Second electric machine 112 includes a rotational connection 142 andthird electric machine 114 also includes a rotational connection 144. Inthe exemplary embodiment shown in FIG. 1, rotational connection 142 isoperatively connected to rotational connection 132 of first differential124 and rotational connection 144 is operatively connected to rotationalconnection 138 of second differential 126. As such, rotational outputcan be transferred between the first differential and the secondelectric motor as well as between the second differential and thirdelectric motor.

In the exemplary embodiment shown in FIG. 1, powertrain 106 alsoincludes third and fourth differentials or differential mechanisms 146and 148, which are operatively connected for drivably engaging one ormore of the plurality of ground-engaging elements of the vehicle. Thirddifferential 146 includes three rotational connections, which arerespectively indicated herein by reference numbers 150, 152 and 154.Similarly, fourth differential 148 includes three rotationalconnections, which are respectively indicated herein by referencenumbers 156, 158 and 160. Rotational connection 130 of firstdifferential 124 is operatively connected to rotational connection 150of third differential 146. Additionally, rotational connection 136 ofsecond differential 126 is operatively connected to rotationalconnection 156 of fourth differential 148.

Rotational output from third and fourth differentials 146 and 148 can betransferred to and/or from the ground-engaging elements (e.g., wheels104A-D) in any suitable manner. For example, as shown in FIG. 1, theground-engaging elements can include final transmissions 162 that aredrivably connected to rotational connections 152, 154, 158 and 160 fortransferring rotational output therefrom. It will be appreciated,however, that any other suitable configuration and/or arrangement couldultimately be used.

One advantage of using a powertrain such at that shown in FIG. 1 is thatthe powertrain provides the capability to substantially independentlycontrol the motive power delivered to each of the two different sides ofthe vehicle. One exemplary method 200 of powering a vehicle using apowertrain in accordance with the present novel concept, such aspowertrain 106, for example, is shown in FIG. 2. Method 200 includesgenerating rotational output using engine ENG, as indicated by arrow202. Method 200 also includes transmitting a first portion of therotational output to first electric machine EM1, as indicated by arrow204. The method also includes transmitting a second portion of therotational output to differential mechanisms DF1 and DF2, as isrespectively indicated by arrows 206 and 208. Method 200 furtherincludes transmitting rotational output from first differentialmechanism DF1 to third differential mechanism DF3, as is indicated byarrow 210. Method 200 also includes transmitting rotational output fromsecond differential mechanism DF2 to fourth differential mechanism DF4,as indicated by arrow 212. Method 200 also includes transmittingrotational output from third and fourth differential mechanisms DF3 andDF4 to the respective ground-engaging elements, as indicated by arrows214.

Method 200 further includes generating electrical power using therotational output transmitted from along arrow 204 to first electricmachine EM1 and transmitting the electrical power to suitable powerelectronics PE, as indicated by dashed arrow 216. Method 200 alsoincludes selectively transmitting electrical power from powerelectronics PE to second and/or third electric machines EM2 and/or EM3,as indicated by dashed arrows 218 and 220, respectively. Method 200further includes transmitting rotational output from second and thirdelectric machines EM2 and EM3 respectively to first and seconddifferential mechanisms DF1 and DF2, as indicated by arrows 222 and 224.This additional rotational output is transmitted to third and fourthdifferential mechanisms DF3 and DF4 for respective transfer to sides SD1and SD2 of the vehicle. Due at least in part to the characteristics ofthis additional rotational output, this method of operation is wellsuited for higher speed operation of the vehicle. Method 200 ca furtherinclude selectively transferring electrical energy to and/or fromstorage device STD, as indicated by dashed arrow 226.

As indicated by directional arrows AR1 in FIG. 2, it will be appreciatedthat both sides SD1 and SD2 of the vehicle are being driven in the samedirection during operation according to method 200. Another benefit ofusing a powertrain in accordance with the present novel concept, such aspowertrain 106, for example, is that under certain operating conditionsit is possible to cause the vehicle to swing around a vertical axisthereof (e.g., an axis through midpoint MPT) to thereby change (e.g.,reverse) the direction of the vehicle. More specifically, by reversingthe rotational direction of one of the second and third electricmachines, the rotational direction of the rotational output from thecorresponding differential mechanisms is likewise reversed. This resultsin the associated ground-engaging elements rotating in the oppositedirection.

One exemplary method of powering a vehicle in such a manner isillustrated in FIG. 2A as method 200′. It will be appreciated thatmethod 200′ is substantially similar to method 200 discussed above withregard to FIG. 2. Method 200′ differs from method 200 in that therotational transmissions represented by arrows 212′, 214′ and 224′ arein the opposing rotational direction. Thus, directional arrows AR1 thatwere associated with third electric machine EM3, second differentialmechanism DF2 and ground-engaging elements GE3 and GE4 have beenreplaced by directional arrows AR2, indicating operation of thesecomponents in the opposing direction. As a result of ground-engagingelements GE1 and GE2 rotating in a first direction and ground-engagingelements GE3 and GE4 rotating in an opposing direction, the vehicle canpivot or otherwise swing about a vertical axis, such as an axisextending through midpoint MPT in FIG. 1, for example.

Turning now to FIG. 3, another exemplary embodiment of a vehicle 300 inaccordance with the present novel concept is shown therein that includesa vehicle structural assembly 302 with a first plurality ofground-engaging elements, such as wheels 304A and 304B, for example,disposed along first side SD1 and a second plurality of ground-engagingelements, such as wheels 304C and 304D, for example, disposed alongsecond side SD2. Vehicle 300 also includes a powertrain 306 that issupported on vehicle structural assembly 302 and is operativelyconnected to drivably engage the first and second pluralities ofground-engaging elements (e.g., wheels 304A-D).

Powertrain 306 is shown in FIG. 3 as including an engine 308, a firstelectric machine 310, a second electric machine 312, a third electricmachine 314 as well as first and second differentials 316 and 318,respectively. It will be appreciated that powertrain 306 issubstantially similar to powertrain 106 shown in and discussed withregard to FIG. 1. As such, the features and elements relating to therotational interconnections thereof are not repeated here.

Vehicle 300 differs from vehicle 100 in that vehicle 300 is equippedwith an all-wheel steering system (not shown) that permitsground-engaging elements on the same side of the vehicle to be steeredat the same angle. A central tire inflation system (not shown) or othersimilar arrangement can optionally be included to assist in maintaininga common rolling radius, if pneumatic wheels are used as ground-engagingelements. Accordingly, the speed of both of the wheels or otherground-engaging elements on a given side of the vehicle will be theapproximately equal. Thus, third and fourth differentials 146 and 148,which were utilized in FIG. 1 to permit ground-engaging elements on agiven side of the vehicle to have different speeds, have been eliminatedfrom powertrain 306. As such, first and second differentials 316 and 318are operatively connected to drivably engage the plurality ofground-engaging elements on respective sides of the vehicle.

First and second differentials 316 and 318 respectively include threerotational connections, as discussed above with regard to differentials124 and 126. For purposes of the present discussion, only one rotationalconnection of each of first and second differentials 316 and 318 isidentified in FIG. 3, which rotational connections are identified byreference numbers 320 and 322. It will be appreciated that first andsecond differentials 316 and 318 can drivably engage the plurality ofground-engaging elements in any suitable manner. For example, driveshafts 324 and 326 can be disposed along opposing sides of the vehiclewith intermediate transmissions 328 and 330, respectively, operativelyengaging rotational connections 320 and 322 of the first and seconddifferentials. The drive shafts can then be operatively connected to theground-engaging elements and any suitable manner, such as by using finaltransmissions 332, for example.

Another exemplary method 400 of powering a vehicle using a powertrain inaccordance with the present novel concept, such as powertrain 306, forexample, is shown in FIG. 4. Method 400 includes generating rotationaloutput using engine ENG, as indicated by arrow 402. Method 400 alsoincludes transmitting a first portion of the rotational output to firstelectric machine EM1, as indicated by arrow 404. The method alsoincludes transmitting a second portion of the rotational output todifferential mechanisms DF1 and DF2, as is respectively indicated byarrows 406 and 408. Method 400 further includes transmitting rotationaloutput from first differential mechanism DF1 to ground-engaging elementsGE1 and GE2 on or along side SD1, as is indicated by arrows 410. Method400 also includes transmitting rotational output from seconddifferential mechanism DF2 to ground-engaging elements GE3 and GE4 on oralong side SD2, as indicated by arrow 412.

Method 400 further includes generating electrical power using therotational output transmitted from along arrow 404 to first electricmachine EM1 and transmitting the electrical power to suitable powerelectronics PE, as indicated by dashed arrow 414. Method 400 alsoincludes selectively transmitting electrical power from powerelectronics PE to second and/or third electric machines EM2 and/or EM3,as indicated by dashed arrows 416 and 418, respectively. Method 400further includes transmitting rotational output from second and thirdelectric machines EM2 and EM3 respectively to first and seconddifferential mechanisms DF1 and DF2, as indicated by arrows 420 and 422.This additional rotational output is transmitted from the differentialmechanisms to the ground-engaging elements along respective sides SD1and SD2 of the vehicle. Furthermore, method 400 can optionally includeselectively transferring electrical energy to and/or from storage deviceSTD, as indicated by dashed arrow 424.

In use on a vehicle that includes an all-wheel steering function, suchas vehicle 300, for example, method 400 can operate to selectively varythe rotational output from one of the second and third electricmachines. This, in turn, varies the rotational output at thecorresponding ground-engaging elements associated with that side of thevehicle, which permits the more effective use of the all-wheel steeringfunction without the use of additional differentials mechanisms, such asthird and fourth differentials 146 and 148 in FIG. 1, for example. Asshown in FIG. 4, second electric machine EM2 is operating at a greaterspeed than third electric machine EM3. Accordingly, directional arrowsAR1 associated with the second electric machine and side SD1 are shownas being of greater length than directional arrows AR3, which areassociated with third electric machine and side SD2.

Turning, now, to FIG. 5, a further exemplary embodiment of a vehicle 500in accordance with the present novel concept is shown that includes avehicle structural assembly 502 with a first plurality ofground-engaging elements, such as wheels 504A and 504B, for example,disposed along first side SD1 and a second plurality of ground-engagingelements, such as wheels 504C and 504D, for example, disposed alongsecond side SD2. Vehicle 500 also includes a powertrain 506 that issupported on vehicle structural assembly 502 and is operativelyconnected to drivably engage the first and second pluralities ofground-engaging elements (e.g., wheels 504A-D).

Powertrain 506 is shown in FIG. 5 as including an engine 508, a firstelectric machine 510, a second electric machine 512, a third electricmachine 514, a first differential 516 and a second differential 518 aswell as driveshafts 520 and 522, intermediate transmissions 524 and 526,and final transmissions 528. As such, it will be appreciated thatpowertrain 506 is substantially similar to powertrain 306 shown in anddiscussed with regard to FIG. 3. Accordingly, the features and elementsrelated to the operation and rotational interconnections thereof are notrepeated here.

Powertrain 506 differs from powertrains 106 and 306 discussed above inthat second and third electric machines 512 and 514 are capable of beingmechanically interconnected to provide additional modes of operationand/or performance characteristics. It will be appreciated that thesecond and third electric Machines can be selectively mechanicallyinterconnected in any suitable manner.

In the exemplary embodiment shown in FIG. 5, second electric machine 512includes a first rotational connection (not numbered) operativelyconnected to first differential 516 and a second rotational connection530 generally opposite the first rotational connection. Similarly, thirdelectric machine 514 includes a second rotational connection 532disposed generally opposite the first rotational connection (notnumbered), which first rotational connection is operatively connected tosecond differential 518. Powertrain 506 also includes a differentialshaft 534 that operatively interconnects second rotational connections530 and 532. Again, it will be appreciated that such interconnectionscan be of any suitable type, kind and/or configuration. For example,fixed ratio transmissions 536 and 538 can be included between thedifferential shaft and the second rotational connections of the secondand third electric machines, respectively. Additionally, one or moreclutches 540 (or other suitable devices) can be provided alongdifferential shaft 534 or otherwise operatively connected between thesecond rotational connections of the second and third electric machines.

Clutch 540 provides the capability for the second rotational connectionsto be selectively rotatable relative to one another, which permits thepowertrain to employ several different modes of operation. As oneexample, permitting relative rotation of the second rotationalconnections of the second and third electric machines providesside-to-side mechanical differential action for accommodating differentspeeds of the two different sides of a vehicle, such as might beexperienced when the vehicle is turning or cornering, for example. Asanother example, the second and third electric machines can be used toadd rotational power to or subtract rotational power from one or both ofthe sides of the vehicle to provide increased directional control of thevehicle (i.e., increased steering capability). As a further example,utilizing the differential shaft and clutch to interconnect the secondrotational connections of the second and third electric machines canresult in a reaction torque being generated between the second and thirdelectric machines that permits the engine to provide motive force to thevehicle without the use of any of the first, second or third electricmachines. As still another example, the second and third electricmachines can be coupled together by way of the differential shaft suchthat reaction torque from one differential can be transmitted to both ofthe second and third electric machines, which can permit additionalelectrical power to be generated thereby.

A further exemplary method 600 of powering a vehicle using a powertrainin accordance with the present novel concept, such as powertrain 506,for example, is shown in FIG. 6. Method 600 includes generatingrotational output using engine ENG, as indicated by arrow 602. Method600 also includes generating rotational output using first electricmachine EM1, as indicated by arrow 604. The method also includestransmitting the rotational output from engine ENG and first electricmachine EM1 to differential mechanisms DF1 and DF2, as is respectivelyindicated by arrows 606 and 608. Method 600 further includes deliveringa first portion of the rotational output from first differentialmechanism DF1 to ground-engaging elements GE1 and GE2 on or along sideSD1, as is indicated by arrows 610. Method 600 also includes deliveringa first portion of the rotational output from second differentialmechanism DF2 to ground-engaging elements GE3 and GE4 on or along sideSD2, as indicated by arrow 612.

Method 600 further includes delivering a second portion of therotational output from first differential mechanism DF1 to secondelectric machine EM2 and delivering a second portion of the rotationaloutput from second differential mechanism DF2 to third electric machineEM3, as is respectively indicated by arrows 614 and 616. Method 600 alsoincludes generating electrical power using electric machines EM2 and EM3from the rotational output delivered thereto from along arrows 614 and616, respectively, and transmitting the electrical power to suitablepower electronics PE, as indicated by dashed arrows 618 and 620. Method600 includes selectively transmitting electrical power from powerelectronics PE to first electric machine EM1, as indicated by dashedarrow 622, which electrical power can be used to generate the rotationaloutput indicated by arrow 604. Furthermore, method 600 can optionallyinclude selectively transferring electrical energy to and/or fromstorage device STD, as indicated by dashed arrow 624.

Method 600 in FIG. 6 illustrates operation of a vehicle in a mode thatis well suited for relatively low vehicle speeds. At such relatively lowspeeds, the torque output capacity of first electric motor EM1 can beutilized, such as to accelerate the vehicle or for use over roughterrain, for example. During such operation, the second and thirdelectric machines are operatively disconnected from one another, asindicated by arrows 626A and 626B, such that first and second electricmachines EM2 and EM3 can rotate independently of one another, asindicated by directional arrows AR4. According, sides SD1 and SD2 of thevehicle can operate at different speeds, as indicated by directionalarrows AR1 and AR3.

Still a further exemplary method 700 of powering a vehicle using apowertrain in accordance with the present novel concept, such aspowertrain 506, for example, is shown in FIG. 6A. Method 700 includesgenerating rotational output using engine ENG, as indicated by arrow702. Method 700 differs from method 600, however, in that method 700permits motive power to be provided to the vehicle without the use ofthe first, second or third electric machines. Method 700 also includedelivering substantially all of the rotational output from engine ENG toat least one of differential mechanisms DF1 and DF2, as is respectivelyindicated by arrows 704 and 706. Method 700 can further includedelivering substantially all of the rotational output from firstdifferential mechanism DF1 to at least one of ground-engaging elementsGE1 and GE2 on or along side SD1, as is indicated by arrows 708. Method700 can also optionally include delivering substantially all of therotational output from second differential mechanism DF2 to one or moreof ground-engaging elements GE3 and GE4 on or along side SD2, asindicated by arrow 710.

In FIG. 6A, method 700 indicates that second and third electric machinesare operatively connected to one another, as indicated by arrow 712. Assuch, rotational output (i.e., reaction torque) from first and seconddifferentials DF1 and DF2 is respectively reacted to the second andthird electric machines, as indicated by arrows 714 and 716. However,because second and third electric machines EM2 and EM3 are operativelycoupled together, no substantial rotational motion occurs between thesecond and third electric machines, as indicated by counter-rotatingdirectional arrows AR5. Even without the operation of the first, secondand third electric machines, however, the vehicle is capable ofoperation under engine power, as indicated by directional arrows AR1.

Another exemplary method 800 of powering a vehicle using a powertrain inaccordance with the present novel concept, such as powertrain 506, forexample, is shown in FIG. 6B. Method 800 includes generating rotationaloutput using engine ENG, as indicated by arrow 802 and generatingrotational output using first electric machine EM1, as indicated byarrow 804. The method also includes delivering substantially all of therotational output from engine ENG and first electric machine EM1 todifferential mechanism DF1, as is indicated by arrow 806. Method 800further includes delivering a first portion of the rotational outputfrom first differential mechanism DF1 to ground-engaging elements GE1and GE2 on or along side SD1, as is indicated by arrows 808.

FIG. 6B represents a method of powering the ground-engaging elements onor along only one side of a vehicle, such as side SD1, for example. Sucha mode of operation may be useful when the vehicle is primarilysupported by only two wheels, such as when the vehicle is stranded on arock or other ground feature, for example. As such, no rotational outputis shown being delivered to second differential DF2 or ground-engagingelements GE3 and GE4 corresponding thereto. As such, no rotationaloutput is being delivered to third electric motor EM3 from the seconddifferential.

Method 800 also includes, however, delivering a portion of therotational output from first differential mechanism DF1 to secondelectric machine EM2, as indicated by arrow 810. Method 800 alsoincludes generating electrical energy using second electric machine EM2from at least a portion of the rotational output delivered thereto andtransmitting the electrical energy to suitable power electronics PE, asindicated by dashed arrow 812. Method 800 also includes selectivelydelivering electrical power to first electric machine EM1 from powerelectronics PE, as indicated by arrow 814.

Method 800 can also optionally include operatively interconnectingsecond and third electric machines EM2 and EM3, such as by engagingclutch 540 of differential shaft 534, for example. As a result of thisinterconnection, rotational motion can be transmitted from secondelectric machine EM2 to third electric machine as indicated bydirectional arrows AR6. Accordingly, additional rotational output fromfirst differential mechanism DF1 can be reacted or otherwise transmittedto third electric machine EM3 via second electric machine EM2, asindicated by arrow 816. As such, method 800 can also optionally includegenerating electrical power using third electric machine EM3 andtransmitting the electrical power to power electronics PE, as indicatedby arrow 818. This additional electrical power can also be transmittedto first electric machine EM1, as indicated by arrow 814, such as forincreasing the rotational output being generated thereby, for example.

With reference to FIG. 7, a vehicle 900 includes a vehicle structuralassembly 902 with a first plurality of ground-engaging elements, such aswheels 904A and 904B, for example, disposed along first side SD1 and asecond plurality of ground-engaging elements, such as wheels 904C and904D, for example, disposed along second side SD2. Vehicle 900 alsoincludes a powertrain 906 that is supported on vehicle structuralassembly 902 and is operatively connected to drivably engage the firstand second pluralities of ground-engaging elements (e.g., wheels904A-D). As shown in FIG. 7, vehicle structural assembly 902 includes apersonnel or operator compartment 906 that is disposed within or atleast partially enclosed by the vehicle structural assembly. It will beappreciated that personnel compartment 906 can be of any suitable shape,size and/or configuration as may be useful for receiving a vehicleoperator and, optionally, one or more additional personnel and/or cargo.As shown in the present exemplary embodiment, compartment 906 caninclude opposing front and rear walls 906A and 906B, respectively, aswell as opposing side walls 906C and 906D.

Powertrain 908 includes a first engine 910 that is supported onstructural assembly 902 along side SD1 thereof, and can be of anysuitable type, kind, size and/or configuration. Powertrain 908 alsoincludes a second engine 912 that is supported on structural assembly902 along side SD2 thereof, and can also be of any suitable type, kind,size and/or configuration. It will be appreciated that first and secondengines 910 and 912 can be of the same or different sizes and/orconfigurations, without limitation. For example, first engine 910 isshown in FIG. 9 as being a four cylinder engine whereas second engine912 is shown as being a six cylinder engine.

Powertrain 908 also includes a first electric machine 914 that isoperatively connected between first and second engines 910 and 912. Itwill be appreciated that the first electric machine can be operativelyconnected between the first and second engines in any suitable manner.For example, in the embodiment shown in FIG. 7, first and second engines910 and 912 respectively include rotational connections 916 and 918.Additionally, first electric machine includes opposing rotationalconnections 920 and 922. A transmission 924 is operatively connectedalong each of rotational connections 916 and 918, and transmissionshafts 926 and 928 are operatively connected between the transmissionsand respective ones of rotational connections 920 and 922. Furthermore,powertrain 908 can also include one or more clutches 930 disposedbetween the first and second engines and the first electric machine.Such clutches can be provided in any suitable manner to operativelydisconnect the first engine from the first electric machine and thesecond engine from the first electric machine.

Powertrain 908 also includes a first differential 932 that is supportedalong side SD1 of the vehicle and a second differential 934 that issupported along side SD2 of the vehicle. First and second differentials932 and 934 are each shown as being operatively connected to firstengine 908, second engine 910 and first electric machine 912 by way oftransmissions 924. As such, a portion of the total combined rotationaloutput from the engines and first electric machine can be transmitted toone or both of the differentials.

First differential 932 includes three rotational connections, which areindicated in FIG. 7 by reference characters 936, 938 and 940. Similarly,second differential 934 includes three rotational connections, which areindicated in FIG. 7 by reference, characters 942, 944 and 946.Rotational connections 936 and 942 are operatively connected to theengines and the first electric machine, as discussed above. Powertrain908 also includes a second electric machine 948 that has two rotationalconnections, which are indicated by reference numbers 950 and 952.Powertrain 908 also includes a third electric machine 954 that also hastwo rotational connections, which are indicated by reference numbers 956and 958. Rotational connections 938 and 952 respectively of firstdifferential 932 and second electric machine 948 are operativelyconnected to one another. Additionally, rotational connections 944 and956 respectively of second differential 934 and third electric machine954 are operatively connected to one another. Rotational connections 940and 946 respectively of first and second differentials 932 and 934 areoperatively connected to drivably engage one or more of the plurality ofground-engaging elements on each of the respective sides of the vehicle,as discussed above with regard to other embodiments. In one exemplaryarrangement, transmission shafts 960, intermediate transmissions 962 andfinal transmissions 964 can be used, such as has been discussed above indetail.

As discussed above with regard to powertrain 506 in FIG. 5, for example,second and third electric machines 948 and 954 are capable of beingmechanically interconnected to provide different modes of operationand/or performance characteristics. It will be appreciated that thesecond and third electric machines can be selectively mechanicallyinterconnected in any suitable manner. In the exemplary embodiment shownin FIG. 7, powertrain 908 includes a differential shaft 966 thatoperatively interconnects rotational connections 952 and 958 of secondand third electric machines 948 and 954, respectively. Again, it will beappreciated that such interconnections can be of any suitable type, kindand/or configuration. For example, transmissions 968 and 970 can beincluded between the differential shaft and the second rotationalconnections of the second and third electric machines, respectively.Additionally, clutches 972 and 974 (or other suitable devices) can beprovided between the respective transmissions and rotational connectionsof the second and third electric machines.

It will be appreciated that powertrain 908 is similar to powertrain 506discussed in detail above and can operate substantially similar thereto.One difference between powertrain 908 and powertrain 506 is that thecomponents of powertrain 908 are disposed outwardly around personnelcompartment 906. Thus, the components of the powertrain are therebycapable of providing additional protection and/or shielding along two ormore of walls 906A-D of the personnel compartment. Another difference isthat a second engine is provided in powertrain 908. As such, the vehiclehas improved capability to withstand damage to one side of the vehicleand still remain drivable, such as while using only about half of thepowertrain components (e.g., those components disposed along theundamaged side of the vehicle). Still a further difference is thatclutch 540 in powertrain 506 can experience differential shaft portionsrotating at full speed in different directions, whereas clutches 972 and974 may experience about half of the speed due to the position thereofalong the operative connection.

Still another exemplary method 1000 of powering a vehicle using apowertrain in accordance with the present novel concept, such aspowertrain 908, for example, is shown in FIG. 8. Method 1000 includesgenerating rotational output using at least one of first engine ENG1, asindicated by arrow 1002, and second engine ENG2, as indicated by arrow1004. Method 1000 also includes transmitting a first portion of therotational output to first electric machine EM1, as indicated by arrow1006. The method also includes transmitting a second portion of therotational output to differential mechanisms DF1 and DF2, as isrespectively indicated by arrows 1008 and 1010. Method 1000 furtherincludes transmitting rotational output from first differentialmechanism DF1 and second differential mechanism DF2 to the respectiveground-engaging elements, as indicated by arrows 1012.

Method 1000 further includes generating electrical power using therotational output transmitted from along arrow 1006 to first electricmachine EM1 and transmitting the electrical power to suitable powerelectronics PE, as indicated by dashed arrow 1014. Method 1000 alsoincludes selectively transmitting electrical power from powerelectronics PE to second and/or third electric machines EM2 and/or EM3,as indicated by dashed arrows 1016 and 1018, respectively. Method 1000further includes transmitting rotational output from second and thirdelectric machines EM2 and EM3 respectively to first and seconddifferential mechanisms DF1 and DF2, as indicated by arrows 1020 and1022. This additional rotational output is transmitted to theground-engaging elements disposed along sides SD1 and SD2 of thevehicle. Furthermore, method 1000 can optionally include selectivelytransferring electrical energy to and/or from storage device STD, asindicated by dashed arrow 1024.

Method 1000 in FIG. 8 illustrates operation of a vehicle in a mode thatis well suited for relatively high speed travel. At such relatively highspeeds, the rotational output of the second and third electric motors isutilized, such as to maintain higher angular velocities of thepowertrain components, for example. During such operation, the secondand third electric machines are operatively disconnected from oneanother, as indicated by arrows 1026A and 1026B, such that first andsecond electric machines EM2 and EM3 can rotate independently of oneanother, as indicated by directional arrows AR4. This provides amechanical differential action such that sides SD1 and SD2 of thevehicle can operate at different speeds, as indicated by directionalarrows AR1 and AR3.

With reference to FIG. 8A, one exemplary method 1100 of generatingelectrical power using a vehicle that includes a powertrain inaccordance with the present novel concept, such as powertrain 908, forexample, includes generating rotational output using at least one offirst and second engines ENG1 and ENG2, as is respectively indicated byarrows 1102 and 1104. Method 1100 also includes transmitting a firstportion of the rotational output to first electric machine EM1, asindicated by arrow 1106. The method also includes transmitting a secondportion of the rotational output to differential mechanisms DF1 and DF2,as is respectively indicated by arrows 1108 and 1110. Method 1100differs from other previously discussed methods in that rather thandelivering rotational output to the ground-engaging elements, method1100 includes transmitting rotational output from first differentialmechanism DF1 and second differential mechanism DF2 to second and thirdelectric machines EM2 and EM3, respectively, as indicated by arrows 1112and 1114. In this case, the ground-engaging elements are in a locked orotherwise non-rotatable condition, which causes substantially all of therotational output from the differential mechanisms to be delivered tothe second and third electric machines, as indicated by directionalarrows AR8.

As indicated by arrows 1116A and 1116B, second and third electricmachines EM2 and EM3 are operatively disconnected from one another. Assuch, the second and third electric machines can rotate independentlyfrom one another, as indicated by directional arrows AR9. Method 1100further includes generating electrical power using the rotational outputtransmitted from along arrow 1106 to first electric machine EM1 andtransmitting the electrical power to suitable power electronics PE, asindicated by dashed arrow 1118. Additionally, method 1100 includesgenerating electrical power using the rotational output transmitted fromalong arrows 1112 and 1114 to second and third electric machines EM2 andEM3, and transmitting the electrical power to suitable power electronicsPE, as indicated by dashed arrows 1120 and 1122, respectively. Method1100 further includes delivering electrical power from power electronicsPE to an external power connection for supplying electrical powerthereto, as indicated by arrow 1124.

While the subject novel concept has been described with reference to theforegoing embodiments and considerable emphasis has been placed hereinon the structures and structural interrelationships between thecomponent parts of the embodiments disclosed, it will be appreciatedthat other embodiments can be made and that many changes can be made inthe embodiments illustrated and described without departing from theprinciples of the subject disclosure. Obviously, modifications andalterations will occur to others upon reading and understanding thepreceding detailed description. Accordingly, it is to be distinctlyunderstood that the foregoing descriptive matter is to be interpretedmerely as illustrative of the present novel concepts and not as alimitation. As such, it is intended that the subject novel concepts beconstrued as including all such modifications and alterations insofar asthey come within the scope of the appended claims and any equivalentsthereof.

1. A vehicle comprising: a vehicle structural assembly having alongitudinally-extending centerline with first and second vehiclestructure portions extending along opposing sides of said centerline; afirst plurality of ground-engaging elements operatively disposed alongsaid first vehicle structure portion on one of said opposing sides ofsaid centerline; a second plurality of ground-engaging elementsoperatively disposed along said second vehicle structure portion on theother of said opposing sides of said centerline; and, a vehiclepowertrain drivably engaging one or more ground-engaging elements ofeach of said first and second pluralities of ground-engaging elements,said vehicle powertrain including: at least one engine including anengine rotational connection; a first electric machine including a firstEM rotational connection operatively connected to said engine rotationalconnection; a second electric machine including a second EM rotationalconnection; a third electric machine including a third EM rotationalconnection; a first differential including first, second and third DFrotational connections, said first DF rotational connection beingoperatively connected to said engine rotational connection and saidfirst EM rotational connection, said second DF rotational connectionbeing operatively connected to said second EM rotational connection, andsaid third DF rotational connection being operatively connected todrivably engage said first plurality of ground-engaging elements on saidone opposing side of said centerline; and, a second differential havingfourth, fifth and sixth DF rotational connections, said fourth DFrotational connection being operatively connected to said enginerotational connection and said first EM rotational connection, saidfifth DF rotational connection being operatively connected to said thirdEM rotational connection, and said sixth DF rotational connection beingoperatively connected to drivably engage said second plurality ofground-engaging elements on said other opposing side of said centerline.2. A vehicle according to claim 1, wherein said vehicle structuralassembly includes an personnel compartment disposed along saidcenterline, and one or more of said engine, said first electric machine,said second electric machine, said third electric machine, said firstdifferential and said second differential is disposed along said vehiclestructural assembly outwardly of said operator compartment and therebyprovides supplemental shielding of said personnel compartment.
 3. Avehicle according to claim 1, wherein said rotational power output ofsaid at least one engine is approximately equal to a combined totalrotational power output of said first, second and third electricmachines such that said at least one engine can drive said first, secondand third electric machines and thereby generate electrical power.
 4. Avehicle according to claim 1, wherein said ground-engaging elements arewheels, and said vehicle structural assembly includes one of a symmetricall-wheel steering system and a non-symmetric all-wheel steering system.5. A vehicle according to claim 1, wherein said second and thirdelectric machines respectively include fourth and fifth EM rotationalconnections, and said powertrain includes a differential shaft isoperatively connected between said fourth and fifth EM connections.
 6. Avehicle according to claim 5, wherein said at least one engine is afirst engine and said rotational connection thereof is a first enginerotational connection, said powertrain includes a second engine thatincludes a second engine rotational connection, and said first electricmachine includes a sixth EM rotational connection operatively connectedto said second engine rotational connection of said second engine.
 7. Avehicle according to claim 1 further comprising an electrical controlsystem in communication with at least said first electric machine, saidsecond electric machine and said third electric machine.
 8. A vehicleaccording to claim 7 further comprising an electrical storage device incommunication said electrical control system and adapted to transferelectrical power to and from at least one of said first electricmachine, said second electric machine and said third electric machine.9. A powertrain adapted to drive associated ground-engaging elementsdisposed along longitudinally-opposing sides of an associated vehicle,said powertrain comprising: at least one engine including an enginerotational connection; a first electric machine including a first EMrotational connection operatively connected to said engine rotationalconnection; a second electric machine including a second EM rotationalconnection; a third electric machine including a third EM rotationalconnection; a first differential mechanism including first, second andthird DF rotational connections, said first DF rotational connectionbeing operatively connected to said engine rotational connection andsaid first EM rotational connection, said second DF rotationalconnection being operatively connected to said second EM rotationalconnection, and said third DF rotational connection operativelyconnected to drivably engage one or more associated ground-engagingelements disposed on one longitudinally-opposing side of the associatedvehicle; and, a second differential mechanism including fourth, fifthand sixth DF rotational connections, said fourth DF rotationalconnection being operatively connected to said engine rotationalconnection and said first EM rotational connection, said fifth DFrotational connection being operatively connected to said third EMrotational connection, and said sixth DF rotational connectionoperatively connected to drivably engage one or more associatedground-engaging elements disposed on the other longitudinally-opposingside of the associated vehicle.
 10. A powertrain according to claim 9,wherein said second and third electric machines respectively includefourth and fifth EM rotational connections, and said powertrain includesa differential shaft is operatively interconnecting said fourth andfifth EM connections.
 11. A powertrain according to claim 10 furthercomprising clutch operatively disposed between said fourth and fifth EMrotational connections, said clutch being operative to selectivelyinterconnect said fourth and fifth EM rotational connections.
 12. Apowertrain according to claim 11, wherein said differential shaftincludes first and second shaft portions and said clutch is operativelyinterconnected between said first and second shaft portions.
 13. Apowertrain according to claim 11, wherein said clutch is a first clutchconnected between said second EM rotational connection and saiddifferential shaft, and said powertrain further comprises a secondclutch connected between said third EM rotational connection and saiddifferential shaft.
 14. A powertrain according to claim 9, wherein saidat least one engine is a first engine and said rotational connectionthereof is a first engine rotational connection, said powertrain furthercomprising a second engine that includes a second engine rotationalconnection, and wherein said first electric machine includes a sixth EMrotational connection operatively connected to said second enginerotational connection of said second engine.
 15. A powertrain accordingto claim 14 further comprising first and second clutches, said firstclutch operatively disposed between said first engine rotationalconnection and said first EM rotational connection for selectivelydisconnecting said first engine and said first electric machine, andsaid second clutch operatively disposed between said second enginerotational connection and said sixth EM rotational connection forselectively disconnecting said second engine and said first electricmachine.
 16. A powertrain according to claim 9 further comprising thirdand fourth differential mechanisms, said third differential mechanismoperatively connected between said third DF rotational connection ofsaid first differential mechanism and said one or more associatedground-engaging elements disposed on said one longitudinally-opposingside of the associated vehicle, and said fourth differential mechanismoperatively connected between said sixth DF rotational connection ofsaid second differential mechanism and said one or more associatedground-engaging elements disposed on said other longitudinally-opposingside of the associated vehicle.
 17. A powertrain according to claim 9further comprising a clutch operatively disposed between said enginerotational connection and said first EM rotational connection, saidclutch being operative to selectively disconnect said engine and firstEM rotational connections.
 18. A method of powering a vehicle, saidmethod comprising: a) providing a vehicle structural assembly includinga longitudinally-extending centerline and opposing vehicle structuresides; b) providing first and second pluralities of ground-engagingelements with said first plurality of ground-engaging elements disposedalong one of said opposing vehicle structure sides and said secondplurality of ground-engaging elements disposed along the other of saidopposing vehicle structure sides; c) providing a vehicle powertrainincluding a first engine, a first electric machine, a second electricmachine, a third electric machine, a first differential and a seconddifferential; d) transmitting rotational output from at least said firstengine to said first and second differentials; e) transmittingrotational output from at least one of said first electric machine andsaid second electric machine to said first differential and transmittingrotational output from at least one of said first electric machine andsaid third electric machine to said second differential; and, f)transmitting rotational output from said first differential to saidfirst plurality of ground-engaging elements to operatively drive saidone of said opposing vehicle structure sides and transmitting rotationaloutput from said second differential to said second plurality ofground-engaging elements to operatively drive said other of saidopposing vehicle structure sides.
 19. A method according to claim 18,wherein providing said vehicle structural assembly in a) includesproviding a vehicle structural assembly that includes a personnelcompartment, and providing said vehicle powertrain in c) includespositioning one or more of said first engine, said first electricmachine, said second electric machine, said third electric machine, saidfirst differential and said second differential outwardly along saidpersonnel compartment for providing supplemental protection to saidpersonnel compartment.
 20. A method according to claim 18, whereintransmitting rotational output in e) includes transmitting rotationaloutput from said engine to said first electric machine and therebygenerating electrical power at said first electric machine, transmittingat least a portion of said electrical power from said first electricmachine to at least one of said second and third electric machines, andtransmitting rotational output from said second electric machine to saidfirst differential and transmitting rotational output from said thirdelectric machine to said second differential.
 21. A method according toclaim 18, wherein transmitting rotational output in e) includestransmitting rotational output from said first differential to saidsecond electric machine and from said second differential to said thirdelectric machine and thereby generating electrical power at said secondand third electric machines, transmitting at least a portion of saidelectrical power from at least one of said second and third electricmachines to said first electric machine, and transmitting rotationaloutput from said engine and said first electric machine to said firstand second differentials.
 22. A method according to claim 19 furthercomprising rotationally affixing said second and third electric machinesrelative to one another, disengaging said first electric machine fromsaid first engine and transmitting rotational output from said engine tosaid first and second pluralities of ground-engaging elements throughsaid first and second differentials to operatively drive the vehiclewithout electrically powering at least one of said first, second andthird electric machines.
 23. A method according to claim 19, whereinproviding said vehicle powertrain in c) includes providing a secondengine and transmitting rotational output in d) includes selectivelytransmitting rotational output from at least one of said first andsecond engines to said first and second differentials.
 24. A method ofgenerating electrical power from a vehicle, said method comprising: a)providing a vehicle structural assembly including alongitudinally-extending centerline and opposing vehicle structuresides; b) providing first and second pluralities of ground-engagingelements with said first plurality of ground-engaging elements disposedalong one of said opposing vehicle structure sides and said secondplurality of ground-engaging elements disposed along the other of saidopposing vehicle structure sides; c) providing a vehicle powertrainincluding a first engine, a first electric machine, a second electricmachine, a third electric machine, a first differential and a seconddifferential; d) rotationally affixing said first and second pluralitiesof ground-engaging members such that rotational output from said firstand second differentials can be respectively transmitted to said secondand third electric machines; e) transmitting rotational output from atleast said first engine to at least one of said first electric machine,said first differential and said second differential; and, f) generatingelectrical power at said at least one of said first, second and thirdelectric machines in response to said rotational output from said firstengine.